Starting unloader for air compressors



Feb. 6, 1923. 1,444,122,

. Y L. F.HOFFM,AN.

STARTING UNLOADER FOR AIR COMPRESSOR S.

map MAY 28, 1921. 3 SHEETS'QSH'EET 1.

A TTORNEY,

Feb, 6, 1923. .I w;

L. F. HOFFMAN.

STARTING UNLOADER FOR AIR COMPRESSOBS.

FILED MAY 2 B, 1921. 3 SHEETSSHEET Z- A TTORNEY.

LEON r. 'HOIEFMAN, or FRANKLIN,

MA'IIC TOOL COMPANY, or NEW PENNSYLVANIA, ASSIGNOR T CHICAGO PNEU- YORK, N. Y., A CORPORATION OF NEW JERSEY.

STARTING- UITLOADER FOR .AIR COMPRESSORS.

Application filed May 28, 1921. Serial No. 473,357.

To all whom it may concern.

Be it known that I, LEON F. HOFFMAN, citizen of the United States, residing at Franklin, in the county of Venango and State of Pennsylvania, have invented certain new and useful Improvements in Starting Unloaders for Air 'Compressors, of

V which the following is a specification.

The object, construction and operation 'of' my improved starting unloader for air compressors, are herein set forth with sufficient clearness to enable those skilled in thearts to which its construction and use respectively relate, to make and use the same.

In the operation of air compressors, it is almost invariably storage tank for the compressed air, which is termed the receiver, and into which the V discharge pipe of the compressor leads. After the initial starting and operation of an air compressor, there is thereafter ,Inaintained a sure of air in this receiver, and each time the compressor is started,.it meets with a resistance equal to this pressure in the receiver. It is desirable therefore that some convenient, expeditious, efficient and automatic means be employed to eliminate or avoid this pressure at the time of starting the compressor, so that it may start with a minimum strain upon the driving power and the various operating parts, of both the air compressor and said power.

This is true with reference to nearly any type of. motive power, and is especially so in case an electric motor is employed for this purpose, in order that the starting torque may be reduced to a minimum; it may be less important, however, in case 40 steam power is employed.

It is the object of this invention to supply means whereby the above results may be attained.

Various forms whereby the mechanical embodiment of my inventive idea may be expressed andpracticed, will be suggested by the drawings and the specification which follows, but, as usual, the precise definition of my invention is to be found in the appended claims.

In said drawingshereof: i

Fig. 1 is ,a side elevation of an electrically-driven air compressor, equipped with my improved starting unloader.

which form a part the practice to provide a practically continuous pres-' tion.

Fig. 3 is a section or portion of said valve with said elements shown in the relation to the main structure which they occupy in the loaded position.

Fig. 4 is an elevation of said control valve, having aspeed actuating device in the form of a centrifugal governor.

Fig. 5 is an elevation of the-reverse side of the regulating valve body.

Fig. 6 is an inverted plan view of the valve which is attached to the stem of the centrifugal governor;

Fig. 7 is aschematic section of the regulating valve and a certain form of air compressor unloader valve showing both these organizations in the unloading and starting positions.

Fig. 8 is a schematic section showing sai-d organizations in the loaded position, as when -the compressor is normally operating.

It will be of assistance to a ready understanding f the construction illustrated and immediately hereafter described, to state that the centrifugal organizationshown in Fig. 4, and which constitutes the actuative mechanism of theoperative elements" within the regulating valve, may be any wellknown form and type of centrifugal governor, such as is commonly used upon steam engines; that which is termed the body of the governor, and the valve used in steam or gas engine practice are dispensed with, and the body and valves shown in Fig. 2 are substituted therefor, said body and its valves being, as previously stated, the primary portion of this invention.

The construction illustrated in said drawings is as follows:

A regulating valve is employed WhlC-ll consists of a body 1 provided with a flange 2 for the reception and attachment of the flange 3 of a centrifugal governor of any suitable type. The relative position and attachment of the centrifugal organization is such that the valve stem 4 thereof extends within whatis termed the receiver chamber 5 of said body 1. Said receiver chamber 5 is divided from the unloader chamber 6 in said body 1 by a partition 7 arranged to governor is effected.

forma seat for a bypass valve 8, which is attached to and actuated by said stem 4.

said unloader chamber 6 to the cylinder 11 of the unloader valve of the air compressor.

Said partition 7 is centrally pierced, and the resulting port is formed at the upper face of the partition, into a seat 12 for the seating of the corresponding face 13 of said by-pass valve 8. Said valve 8 terminates in a triangular guide 8'Fig. 6which has free longitudinal movement through said port of the wall 7 the lower end of said guide 8 is adapted to contact with the upper adjacent end of the valve-stem 16, as hereafter stated. The triangular form of said guide 8 is for the purpose of allowing a free passage of air along the same from chamber'5 to chamber 6.

lVithin the bottom wall of body 1 is introduced a valve seat bushing for the-support and reception of a relief valve 15. Said seat 14 is externally threaded to enter a correspondingly threaded port therefor in said body 1. The threaded portion of this seat is somewhat elongated, whereby it is adapt; ed to have a certain amount of longitudinal adjustment, for a purpose that will later appear.

The valve 15 is provided with a stem 16 which projects through said seat and its inner end is surrounded with a compression spring 17 which, after being somewhat compressed, is secured in position by means .of a washer 18 and a cotter pin 19, whereby said valve is firmly but yieldably retained uponits seat in said bushing 14.

The centrifugal organization may be op-- erated either from the crank-shaft of the compressor, or from the shaft of the motor, but for various reasons, the crank-shaft of the air compressor is preferred.

In Fig. 1 is shown a belt 21 which passes around a pulley 22 upon the crank-shaft 23 of the compressor and the pulley 24 of the centrifugal organization, whereby transmission of motion from the crank-shaft of the compressor to the pulley shaft of the When the air compressor the stem 4 of the governor occupies a position such as to hold the bypass valve 8 in the position shown in Figs. 1 and 7, which is the unseated position of said valve 8, and in this position air passes from the receiver through the regulator valve to the cylinder 11 of the unloader valve, as shown in Fig.

be fully compressed and is not running,

7 The result of this is to hold the valve of the compressor open so that instead of said compressor valve performing its natural function, there is a regurgitative action of the air at thisyalve, and hence no power is consumed or required in compressing air and forcing it into the receiver against the pressure therein, and this is what is termed the unloaded state ofthe compressor; the only power required to operate it is'such as to'overcome mechanical friction.

\Vhen the motive power generator,in this case the motorhas arrived at normal speed, the action ofthe centrifugal organization will cause the stem 4.- and the thereto-attached valve 8 to move downward so justable bushing 14 and seat for said valve 15, is, to eliminate the necessity of accurately gauging the distance between seat 12 and the seat 15, and also to provide ample room for the spring 17 so that it will never prevent the proper seating of the by-pass valve 8. This adjustment also provides means for regulating and determining to a certain extent, the time at which air will be released from the unloader-cylinder. 1

Many types of unloaders for air compressors are adapted to be operated by means of my improved regulating valve. However, for the sake of clearness and completeness of this description, I will explain the unloader valve illustrated in the drawing.

respective forks 28 of said actuator areyieldably supported out of contact with the valve plate 29 by the compression-spring 30, as shown in Fig. 8. V

An actuating cylinder 11 is carried by the cover 31 for'the valve port; said cylinder 1s"concentric with the stud 27, and in the same is mounted a piston 32, having a bifurcate lower end which bears upon the upper end of said actuator; the upper end of said piston is provided with a suitable packing 33, whereby said piston is made suitable for actuation by compressed air.

valve 29,'it is moved from its seat to the retaining member 35, in opposition tothe compression springs 36. As soon as air is closing of said valve, whereby said unloaderv released from said cylinder, the spring 30 returns the actuator 36 to its upward, normal position.

I claim the following:

1. A starting unloader for air compressors comprising, in combinatioman unloader for said compressor, asupply of air under pressure, a conduit for the passage of air from said supply to said unloader by which said unloader is actuated into its unloading position, when the compressor is stopped, a normally-open valve interposed in said con duit, centrifugal means driven by the compressor closing said valve after the compressor is started bywhich said passage of air is arrested, and adjustable means 1'e leasing the residual air in said conduit "between said valve and said unloader upon the is permitted to discontinue its unloading functions.

2. A starting, unloader for air compres-.

the compressor has started, and adjustable means automatically'releasing the actuative air from the unloader upon the closing of saidvalve.

3. In a starting unloader for air compressors, a pneumatically-actuated unloader for the compressor, a source of actuative air for said unloader, a conduit for the passage. of air from .said source to said unloader, a regulating valve organization interposed in said conduit comprising a body having a' chamber therein which is divided by a partition wall into two compartments from one of which, termed the receiver compartment, said conduit'leads to said source of actuative air, and from the other, termed the unloader compartment, said conduit leads to said unloader, said partition wall having as a feature thereof a port connecting said compartments, a valve adapted to open and close said port. centrifugal means operated by the compressor connected to said valve and arranged to hold the same in the open position when the compressor is stopped and to actuate said valve into the closed position when the compressor has reached a pre-determined speed, and a spring-closed relief valve for said unloader compartment actuable to the open position by the closing movement of said first-mentioned valve for the release of actuative air from said unloader.v

4:. In a starting unloader for air com-,

pressors, a pneumatically-actuable unloader for the compressor, a source of actuative air for said unloader, a conduit for the pas sage of said actuative air from said source to said unloader, a regulating valve organization interposed in said conduit comprising a body having a chamber which is divided by a partition wall into two compartments from one of which, termed the receiver compartment, said conduit leads to said source of actuative air, and from the other, termed the unloader compartment, said conduit leads to said unloader, said partition wall having as a feature thereof a port connecting said compartments, a valve adapted to open and to close said port, centrifugal means operated by the compressor connected to said valve arranged to hold the same in the open position when the compressor is stopped and to actuate said valve to its closed position when the compressor has reached a predetermined speed, a normally closed, yieldable relief valve for said unloader compartment actuable to its open,

relief position by the closing action of said first mentioned valve, and an adjustable mounting for said relief valve whereby its opening movement may be varied relativeto the closing movement of said first-men tioned valve.

5. In a starting unloader for air compressors comprising, in combination, an air compressor provided with an unloader, a supply of air under pressure, a conduit for the passage of air from said supply of air to the unloader, a normally open valve interposed in said conduit permitting the passage of air from said supply to said unloader to actuate the same into its unloading position when the compressor 'is not running, speed-actuated means closing said valve to discontinue said passage of air at a predetermined speed of said compressor,

and adjustable means releasing the actuating air from said unloader cylinder upon the closing of said valve.

6. In a starting unloader for air compressors, apneumatically-actuable unloader for said compressor, a source of actuative air for said unloader, a conduit for the passage of said actuative air from said source to said unloader, a regulating valve organization interposed in said conduit comprising a body having a chamber which is divided by a partition wall into two compartments, from one of which, termed the receiver compartment, said conduit leads to said source of actuative air, and from the other, termed the unloader' compartment, said conduit leads to said unloader, said partition wall having as a feature thereof a port connecting said compartments, a valve adapted to open and to close said port,

' the wall of said unloader compartment having as a feature thereof a release port leading to the atmosphere, a spring-actuated valve normally closing said release port,

and centrifugal means operated by the compressor connected to said first-mentioned valve arranged to hold the same in the open position when the compressor is stopped and to actuate the same'to the closed position when the compressor has reached a pre-determined speed; said spring-actuated valve being adapted to be actuated to its open position by the closing action of said firstmentioned valve. Y i In testimony whereof I afiix my signature in presence of two witnesses.

LEON F. HOFFMAN.

Witnesses:

L.- D. DoRWoRTH, T. V. FORBES. 

